Endoscope suitable for autoclaving

ABSTRACT

An endoscope suitable for autoclaving in accordance with the present invention has a barrier that separates an interior from an exterior. When the barrier is located at a predetermined position, consideration is taken into a displacement of the barrier between the position of the barrier observed before start of autoclaving and the position thereof observed after completion of the autoclaving during which predetermined pressure is applied and a thermal load is imposed.

This application claims the benefit of Japanese Application No.2000-257723 filed in Japan on Aug. 28, 2000 the contents of which areincorporated by this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an endoscope capable of undergoingautoclaving (sterilization with high-temperature high-pressure steam)when the endoscope must be disinfected or sterilized after being used.

2. Description of the Related Art

Endoscopes are widely employed in the field of medicine these days. Theendoscope has an elongated insertion member inserted into a body cavityfor the purpose of observing a deep region in the body cavity, or theendoscope is used in combination with a therapeutic instrument, ifnecessary, to perform a cure or remedy. For the medical-purposeendoscope, it is essential to reliably disinfect or sterilize a usedendoscope.

Recently, autoclaving (sterilization with high-temperature high-pressuresteam) is getting mainstream in sterilization of medical equipment. Thisis because autoclaving is no labor-intensive but low-cost, and medicalequipment can be used immediately after it is autoclaved.

Typical conditions for autoclaving are stipulated in the U.S. standardANSI/AAMI ST37-1992 recommended by the American National StandardsInstitute and published from the Association for the Advancement ofMedical Instrumentation. The standard stipulates that, for example, apre-vacuum sterilization process should be performed at 132° C. for 4min and a gravity settling sterilization process should be performed at132° C. for 10 min.

The above environmental conditions for autoclaving are quite severe forendoscopes that are precision electronic apparatuses. In order torealize an endoscope that withstands the environment to undergoautoclaving, unlike an endoscope that shall be reused after subjected toa general disinfecting or sterilizing means, various measures must betaken against high pressure, high temperature, steam, and so on.

Moreover, an existing endoscope has push-button switches such as remotecontrol switches, which are used to control the actions of externalunits placed outside the endoscope, exposed on a control sectionthereof. For example, a push-button switch described in JapaneseUnexamined Utility Model Publication No. 2-58401 consists of a switch, apressing member, and a presser. The switch is exposed on the controlsection. The pressing member is a waterproof film that has elasticityand shields the switch to keep the switch watertight. The presser thatpresses the switch is fixed to the pressing member and opposed to theswitch.

In general, however, the external pressure of an endoscope is relativelyhigher than the internal pressure thereof after the endoscope undergoesa pressurization step or a dry step that is one step of autoclaving(sterilization with high-temperature high-pressure steam). Due to adifference in pressure between the interior of the endoscope and theexterior thereof, force works on the endoscope from the exterior of theendoscope to the interior thereof. In the endoscope described in theJapanese Unexamined Utility Model Publication No. 2-58401, the softpressing member elastically deforms toward the interior of theendoscope. An end of the presser fixed to the pressing member approachesthe switch. In some cases, the end of the presser may press the switch.

Moreover, if the end of the presser presses the switch to a greatextent, a very small stem that forms the switch may deform permanently.In particular, at the pressurization step, not only a load derivedpressure but also a thermal load derived from high temperature may beimposed on the switch. In some cases, therefore, the switch itself maydeform.

Furthermore, after the dry step is completed, if the endoscope is leftas it is for a prolonged period of time, force works on the endoscopefrom the exterior of the endoscope to the interior thereof for theprolonged period of time. Consequently, the stem may be deformedpermanently. Eventually, when a user presses the push-button switch, theuser may have a different sense of touch.

Moreover, an existing endoscope has elongated resin tubes incorporatedin an insertion member thereof. The tubes are used as anaeration/perfusion channel, a therapeutic instrument passage channel,and others. When the endoscope is autoclaved, since the interior of theendoscope is sealed, if the resin tubes expand to increase their outerdiameters due to pressure applied at the pressurization step, the otherbuilt-in components of the endoscope may be pressured. If one of thebuilt-in components, for example, a light guide is pressured, suchaccident may happen that a fiber bundle over which illumination light ispropagated is broken in the middle thereof.

There is a demand for an endoscope in which even if resin tubes expandat a pressurization step of autoclaving, the resin tubes do not pressurethe other built-in components after completion of the autoclaving. Alsodemanded is an endoscope in which even if a flexible tube contracts todecrease its inner diameter due to pressure applied at a pressurizationstep, at least after the autoclaving is completed, resin tubes do notpressure the other built-in components. Also demanded is an endoscope inwhich resin tubes will not pressure the other built-in components evenat the pressurization step.

Moreover, an existing endoscope has, for example, a softbreakage-of-insertion member preventing member engaged with theperiphery of a flexible tube, which serves as part of the surface of ahousing of the endoscope, in order to keep the flexible tubefluid-tight. In an atmospheric-pressure environment, fluid will notinvade into the interior of the endoscope through the junction betweenthe breakage-of-insertion member preventing member and flexible tube.When the endoscope is autoclaved, steam invades into the junctionbetween the breakage-of-insertion member preventing member and flexibletube, and eventually into the interior of the endoscope because ofpressure applied at a pressurization step.

At a dry step, on the other hand, the internal pressure of an autoclaveis negative because of decompression. However, if the junction betweenthe breakage-of-insertion member preventing member and flexible tube iskept fluid-tight, there is a fear that steam having invaded into thejunction and the interior of the endoscope at the pressurization stepmay stagnate in the junction and the interior of the endoscope. Inparticular, if steam stagnates in the junction between thebreakage-of-insertion member preventing member and flexible tube, ametallic part employed in the junction may corrode.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide anendoscope in which even if a pressing member is deformed due toautoclaving, the pressing member will not press a switch.

Another object of the present invention is to provide an endoscope whoseswitches are prevented from deforming due to autoclaving.

Still another object of the present invention is to provide an endoscopewhose resin tubes will not pressure the other built-in components aftercompletion of a pressurization step or a sterilization step that is onestep of autoclaving.

Still another object of the present invention is to provide an endoscopein which a fluid-tight seal between an elastic member and the surface ofthe housing of the endoscope is freed at a dry step that is one step ofautoclaving in order to prevent corrosion of the junction between theelastic member and the housing.

Briefly, an endoscope suitable for autoclaving in accordance with thepresent invention has a soft barrier that separates an interior from anexterior. When the barrier is located at a predetermined position,consideration is taken into a displacement of the barrier between theposition of the barrier observed before start of autoclaving and theposition thereof observed after completion of the autoclaving duringwhich a load arising from predetermined pressure and a predeterminedthermal load are imposed on the barrier. Therefore, even if the barrieris displaced, a member placed near the barrier is prevented from beingbroken due to the displacement.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory diagram showing the configuration of anendoscope system;

FIG. 2A is a cross sectional view showing a push-button switch underatmospheric pressure;

FIG. 2B is a cross sectional view showing the push-button switch thathas undergone a pressurization step or dry step of autoclaving and thathas entered a state different from the state shown in FIG. 2A;

FIG. 3A is a cross sectional view for explaining the structure of apush-button switch whose waterproof film has the capability of a presserand which has the pressure thus formed as an integral part of a pressingmember thereof;

FIG. 3B is a cross sectional view of a push-button switch having anelastic member placed inside a waterproof film thereof;

FIG. 4A is a cross sectional view showing a flexible tube in an initialstate in which an endoscope is not yet put in an autoclave;

FIG. 4B is a cross sectional view showing the flexible tube in a statein which the external pressure of the endoscope that has been put in theautoclave with the flexible tube held in the state shown in FIG. 4A andthat has undergone a sterilization step or a drying step is higher thanthe internal pressure thereof;

FIG. 5A is a longitudinal sectional view showing the state of a controlsection of the endoscope in an atmospheric-pressure environment; and

FIG. 5B is a longitudinal sectional view showing the state of thecontrol section of the endoscope attained when the external pressure ofthe endoscope that has been put in the autoclave with the controlsection held in the state shown in FIG. 5A is lower than the internalpressure thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, an embodiment of the present invention willbe described below.

As shown in FIG. 1, an endoscope system 1 consists mainly of anendoscope 2, a light source apparatus 3, a video processor 5, and amonitor 6. The endoscope 2 is so constituted that can be cleaned andthen sterilized with high-temperature high-pressure steam (hereinafter,autoclaved) after used for observation or operation.

The endoscope 2 has an imaging means that is not shown. The endoscope 2can be detachably connected to the light source apparatus 3, wherebyillumination light is propagated to a light guide that runs through theendoscope 2. The endoscope 2 and video processor 5 are connected over asignal cable 4. The video processor 5 controls the imaging meansincorporated in the endoscope 2, processes a signal sent from theimaging means to produce a standard video signal, and transfers thevideo signal to the monitor 6. Consequently, an endoscopic image isdisplayed on the monitor 6.

The endoscope 2 consists mainly of an insertion member 7, a controlsection 8, a universal cord 9, and a connector unit 10. The insertionmember is elongated and flexible. The control section 8 is fixed to theproximal end of the insertion member 7. The universal cord 9 havingflexibility is extended from the lateral part of the control section 8.The connector unit 10 fixed to an end of the universal cord 9 isconnected to the light source apparatus 3 so that it can be disconnectedfreely.

An electric connector 11 to or from which the signal cable 4 that iscoupled to the video processor 5 can be freely coupled or uncoupled isformed on the lateral part of the connector unit 10.

An breakage-of-insertion member preventing member 12 including anelastic member is mounted on the joint between the insertion member 7and control section 8 in order to prevent abrupt bending of the joint.Moreover, an breakage-of-control section preventing member 13 includingan elastic member is mounted on the joint between the control section 8and universal cord 9 in order to present abrupt bending of the joint.Furthermore, an anti-connector unit breakage member 14 including anelastic member is mounted on the joint between the universal cord 9 andconnector unit 10 in order to prevent abrupt bending of the joint.

The insertion member 7 consists of a flexible tube 15, a bending section16 distal to the flexible tube 15, and a distal part 17 distal to thebending section. The flexible tube 15 is a flexible soft member. Thebending section 16 can be bent by manipulating an angling knob that willbe described later and that is exposed on the control section 8. Anobservation optical system and an illumination optical system that arenot shown are incorporated in the distal part 17.

The control section 8 has an aeration/perfusion button 21, a suctionbutton 22, an angling knob 23, push-button switches 24, and atherapeutic instrument insertion port 25 and so on. Theaeration/perfusion button 21 is used to perform aeration or perfusion.The suction button 22 is used to perform suction. The angling knob 23 isused to bend the bending section 16. The push-button switches 24 are aplurality of remote control switches used to remotely control the videoprocessor 5. The therapeutic instrument insertion port 25 is an openingthat opens into a therapeutic instrument channel.

An aeration/perfusion nozzle which is not shown and from which cleaningfluid or gas is jetted out to an observation window included in theobservation optical system, which is not shown, during aeration orperfusion is placed in the distal part 17. Moreover, a suction port thatis not shown and that is a distal opening of the therapeutic instrumentchannel that is not shown opens on the space in the distal part 17. Atherapeutic instrument is passed through the therapeutic instrumentchannel formed in the insertion member 7 or fluid is sucked from a bodycavity through the therapeutic instrument channel formed therein.Moreover, a fluid supply port which is not shown and through which fluidis jetted out opens toward an object of observation.

The connector unit 10 has an air supply base 26, a water supply tankpressurization base 28, a fluid supply base 29, a suction base 30, andan injection base 31. The air supply base 26 is connected to an airsource, which is not shown and incorporated in the light sourceapparatus 3, so that it can be disconnected freely. The water supplytank pressurization base 28 and fluid supply base 29 are connected to awater tank 27, which is a fluid source, so that they can be disconnectedfreely. The suction base 30 is connected to a suction device that is notshown and that sucks fluid through the suction port in the distal part17. The injection base 31 is connected to a water source that is notshown and that supplies water through the fluid supply port present inthe distal part 17.

Moreover, the connector unit 10 has a ground base 32 through whichhigh-frequency leakage current is fed back to a diathermy device if theleakage current flows through the endoscope during diathermy.

The electric connector 11 has an air vent hole that is not shown andthat links the interior of the endoscope 2 and the exterior thereof.Moreover, a pressure regulating valve-inclusive waterproof cap 33 isfreely detachably attached to the electric connector 11. The waterproofcap 33 has a pressure regulating valve that is not shown and that servesas a linking means. The pressure regulating valve opens when theinternal pressure of the endoscope 2 is higher than the externalpressure thereof. When the external pressure of the endoscope 2 ishigher than the internal pressure, the pressure regulating valve isclosed in order to keep the interior of the endoscope 2 fluid-tight andshut out the interior thereof from the exterior thereof.

For autoclaving, the endoscope 2 is stowed in a sterilization casing(hereinafter, casing) 34.

The casing 34 consists of a tray 35 in which the endoscope 2 is stowedand a lid member 36 that covers the tray 35. Each of the tray 35 and lidmember 36 has a plurality of pores that are not shown. Duringautoclaving, steam passes through the pores.

The tray 35 has a restriction dent, which is not shown and shaped inconformity with the endoscope 2, formed therein. The components of theendoscope 2 are settled in predetermined places in the restriction dent.The restriction dent includes an insertion-member restriction dent whichis not shown and in which the insertion member 7 having flexibility isfitted.

Typical conditions for autoclaving are stipulated in the U.S. standardANSI/AAMI ST37-1992 recommended by the American National StandardsInstitute and published from the Association for the Advancement ofMedical Instrumentation. The standard stipulates that, for example, apre-vacuum sterilization process should be performed at 132° C. for 4min and a gravity settling sterilization process should be performed at132° C. for 10 min.

The condition of the temperature for autoclaving varies depending on themodel of an autoclave or the time required for the autoclaving.Generally, the temperature for autoclaving ranges from about 115° C. toabout 138° C. Some types of autoclaves can be set to about 142° C. Thetime required for autoclaving varies depending on the condition of thetemperature for autoclaving. Generally, the time ranges from about 3 minto about 60 min. Some types of autoclaves can be set to about 100 min.

The pressure in a sterilization chamber for autoclaving is generally setto a value that deviates from the atmospheric pressure by about +0.2[MPa].

A general pre-vacuum high-temperature high-pressure steam sterilizationprocess includes a pre-vacuum step and a sterilization step. At thepre-vacuum step, a sterilization chamber in which equipment to besterilized is put is decompressed in preparation for sterilization. Atthe sterilization step succeeding the pre-vacuum step, high-pressurehigh-temperature steam is fed to the sterilization chamber for thepurpose of sterilization.

The pre-vacuum step is needed in order to infiltrate steam into everycorner of equipment to be sterilized at the succeeding sterilizationstep. When the sterilization chamber is decompressed, high-pressurehigh-temperature steam permeates the whole equipment to be sterilized.The pressure in the sterilization chamber for the pre-vacuum step isgenerally set to a value that deviates from the atmospheric pressure bya value ranging from about −0.07 [MPa] to about −0.09 [MPa].

Some sterilization processes include a dry step. At the dry stepsucceeding the sterilization step, the sterilization chamber isdecompressed again in order to dry the sterilized equipment to besterilized. At the dry step, the sterilization chamber is decompressedin order to eliminate steam from the sterilization chamber. Thisfacilitates drying of the equipment to be sterilized placed in thesterilization chamber. The pressure in the sterilization chamber for thedry step is generally set to a value that deviates from the atmosphericpressure by a value ranging about −0.07 to −0.09 [MPa].

When the endoscope 2 is autoclaved, the pressure regulatingvalve-inclusive waterproof cap 33 is attached to the electric connector11. In this state, the pressure regulating valve, which is not shown, ofthe waterproof cap 33 is closed. Namely, the air vent hole is blocked bythe waterproof cap 33, and the interior of the endoscope 2 is sealed tobe watertight and shut out from the exterior thereof.

When a sterilization process includes the pre-vacuum step, the pressurein the sterilization chamber is decreased at the pre-vacuum step.Consequently, a difference in pressure occurs between the interior andexterior of the endoscope 2. Namely, the external pressure of theendoscope 2 gets lower than the internal pressure thereof. This causesthe pressure regulating valve to open. The interior of the endoscopecommunicates with the exterior thereof through the air vent hole.Consequently, a large difference will not be produced between theinternal pressure of the endoscope 2 and the pressure in thesterilization chamber. Consequently, the endoscope 2 is protected frombeing broken due to a difference in pressure.

When the sterilization chamber is pressurized at the sterilization step,if a difference in pressure occurs between the interior and exterior ofthe endoscope, that is, the external pressure of the endoscope 2 getshigher than the internal pressure thereof, the pressure regulating valvecloses. Consequently, high-pressure high-temperature steam cannotactively invade into the interior of the endoscope 2 through the airvent hole via the waterproof cap 33. However, the high-pressurehigh-temperature steam gradually invades into the interior of theendoscope via a sheathing of the flexible tube or O rings. The sheathingis made of a high polymer material, while the O rings are made of afluorocarbon rubber. The O rings serving as sealing means are includedin joints which are integral parts of the housing of the endoscope 2.

Incidentally, pressure that is the sum of pressure released duringdecompression at the pre-vacuum step and pressure applied at thesterilization step works on the housing of the endoscope 2 from theexterior of the endoscope to the interior thereof.

When the sterilization step is succeeded by a decompression step, thepressure in the sterilization chamber is decreased at the decompressionstep. Consequently, a difference in pressure occurs between the interiorand exterior of the endoscope 2, that is, the external pressure of theendoscope 2 gets lower than the internal pressure thereof. This causesthe pressure regulating valve to open almost at the same time.Consequently, the interior of the endoscope 2 communicates with theexterior thereof through the air vent hole. Therefore, a largedifference will not be produced between the internal pressure of theendoscope 2 and the pressure in the sterilization chamber. Thus, theendoscope 2 is protected from being broken due to a difference inpressure.

Thereafter, the internal pressure of the endoscope becomes equal to theexternal pressure thereof, and the pressure regulating valve closes.When the decompression step is completed, the pressure in thesterilization chamber is equal to the atmospheric pressure.

When all the steps of autoclaving are completed as mentioned above,pressure that equals pressure released at the decompression step workson the housing of the endoscope from the exterior of the endoscope tothe interior thereof.

Finally, the waterproof cap 33 is detached from the electric connector11. Consequently, the interior of the endoscope 2 communicates with theexterior thereof through the air vent hole. The internal pressure of theendoscope 2 becomes equal to the atmospheric pressure. Consequently, theendoscope 2 is unloaded from the pressure that has worked on thehousing.

After autoclaving is completed as mentioned above, the endoscope 2 isreused for endoscopic examination.

Referring to FIG. 2A to FIG. 3B, the detailed structure of thepush-button switches 24 included in the endoscope 2 capable of beingautoclaved will be described below.

As shown in FIG. 2A and FIG. 2B, each push-button switch 24 consistsmainly of a switch 41 and a pressing member 42. The switch 41 can besterilized with high-temperature high-pressure steam. The pressingmember 42 covers the switch 41 to keep the switch 41 watertight, andincludes a presser that will be described later. The pressing member 42can elastically be deformed in order to actuate the switch 41, and canbe displaced relative to the switch 41.

The pressing member 42 consists mainly of a waterproof film 43 and apresser 44. The waterproof film 43 serves as a barrier that can beelastically deformed when touched directly by an operator. The presser44 is formed as an integral part of the waterproof film 43, and extendedto face the switch 41 so that it can press the switch 41. The waterprooffilm 43 is fixed to a control section housing 8 a that is an integralpart of the control section 8 so that the waterproof film 43 will bekept fluid-tight.

A stem that is not shown is incorporated in the switch 41. When the stemdeforms, the off and on states of the switch 41 are switched. The stemis made of a thin metal or a resin material so that the stem can bedeformed easily. The waterproof film 43 is made of a soft rubbermaterial. Moreover, the presser 44 is made of a hard metallic materialor a resin material.

The waterproof film 43 can be changed in shape such that, like apush-button switch 24 b shown in FIG. 3A, the waterproof film 43 mayhave the capability of the presser 44. Thus, the pressing member 42 maybe structured so that it will partly serve as the presser 44 and bedevoid of the presser 44.

Elastic force exerted by the pressing member 42 included in thepush-button switch 24 depends on the hardness of a rubber made into thewaterproof film 43. Like a push-button switch 24 c shown in FIG. 3B, forexample, a coil spring 45 may be adopted as an elastic member andengaged with the inner surface of the waterproof film 43. Elastic forceexerted by the coil spring may be thus utilized.

As shown in FIG. 2A, the position of an end of the presser 44 in anatmospheric-pressure environment shall be an initial reference position.A distance from a solid line L1 extended from the initial referenceposition to the top of the switch 41 shall be Xsp.

In FIG. 2A, Xsp may assume a positive value, that is, a gap may bepresent between the end of the presser 44 and the top of the switch 41,or Xsp may be zero. When Xsp is zero, it means that the end of thepresser 44 is in contact with the top of the switch 41, or the presser44 constrains the switch 41 to move inward. The switch 41 itself canmove by a distance Xsw. That is to say, the distance Xsw is representedas a stroke of the switch 41.

After a pressurization step or a dry step of autoclaving is completed,the external pressure of the endoscope 2 is higher than the internalpressure thereof. Due to the difference in pressure between the interiorof the endoscope and the exterior thereof, force works on the endoscope2 from the exterior of the endoscope 2 to the interior thereof.

As shown in FIG. 2B, the soft waterproof film 43 elastically deformsinward or to the interior of the endoscope 2. Along with the elasticdeformation, the end of the presser 44 moves by a distance Xac from theinitial reference position indicated with an alternate long and twodotted chain line L1 to a position indicated with a solid line L2. Thedistance Xac is a displacement of the end of the presser 44 from theinitial reference position.

Herein, the position of the end of the presser 44 observed before startof autoclaving shall be determined to meet Xac>Xsp. In this case, afterthe pressurization step or dry step of autoclaving is completed, thepresser 44 keeps constraining the switch 41 to move inward. Inparticular, at the pressurization step, the stem that is not shown andincorporated in the switch 41 deforms permanently due to two loads; aload derived from pressure and a high-temperature thermal load.Consequently, at the time of endoscopic examination, there can bedeterioration in the push-button switch manipulation or a conductionfailure.

Moreover, after the dry step is completed, the presser 44 constrains theswitch 41 to move inward for a longer time than it does when thepush-button switch is manipulated normally. In other words, the switch41 is put in a severer state than it is when the push-button switch ismanipulated normally. Therefore, the stem that is incorporated in theswitch 41 and not shown may be deformed permanently.

Moreover, depending on a resin material made into the pressing member42, the pressing member 42 itself may deform permanently due to pressureapplied at the pressurization step and a high-temperature thermal loadimposed thereat. Because of the permanent deformation, even afterautoclaving is completed, the presser 44 may keep constraining theswitch 41 to move inward.

In consideration of the above fact, according to the present embodiment,the distance between the initial reference position observed in anatmospheric-pressure environment and the top of the switch 41 isdetermined to have a relationship expressed below:

Xac≦Xsp  (1)

where Xac denotes a displacement of the end of the presser from theinitial reference position, and Xsp denotes the distance between theinitial reference position of the end of the presser and the top of theswitch.

When the pressing member is positioned, consideration is taken into theposition of the presser observed before start of autoclaving.Consequently, the presser can be surely prevented from constraining theswitch to move inward due to pressure applied after completion of thepressurization step or dry step of autoclaving.

Incidentally, the displacement Xac of the pressing member 42 from theinitial reference position thereof is a distance by which the pressingmember 42 moves only due to pressure applied after completion of thepressurization step or dry step. Thus, when an operator who uses theendoscope 2 presses the waterproof film 43, the presser 44 can move by adistance Xsp+Xsw. At this time, the switch 41 is moved inward by thedistance Xsw and thus moved normally.

Specifically, to begin with, an initial state attained before start ofautoclaving will be discussed. In the initial state, the externalpressure of the endoscope 2 and the internal pressure thereof are nearlyequal to the atmospheric pressure (abbreviated as Pa). So, the pressureregulating valve incorporated in the endoscope 2 remains closed and adifference in pressure does not occur between the exterior of theendoscope 2 and the interior thereof. As a result, force oriented fromthe exterior of the endoscope to the interior thereof does not work onthe endoscope 2. The waterproof film 43 does not therefore deform.

Next, the pre-vacuum step will be discussed.

At the pre-vacuum step, the internal pressure of an autoclave isnegative (the negative pressure shall be abbreviated as −Pv1). At thistime, a difference in pressure occurs between the exterior of theendoscope 2 and the interior thereof. Due to the difference in pressure,the pressure regulating valve opens and the internal pressure of theendoscope 2 is regulated. When the pre-vacuum step is completed, thedifference in pressure between the exterior of the endoscope 2 and theinterior thereof is nullified. In other words, the external pressure ofthe endoscope 2 and the internal pressure thereof become nearly equal toeach other or become negative (the negative pressure is −Pv1). In thisstate, there is no difference in pressure between the exterior of theendoscope 2 and the interior thereof. and force oriented from theexterior of the endoscope to the interior thereof does not work on theendoscope 2. The waterproof film 43 does not therefore deform.

Next, the sterilization step will be discussed.

At the sterilization step, the interior of an autoclave is pressurized(the pressure shall be abbreviated as Pac). At this time, the externalpressure of the endoscope 2 is Pac, and the internal pressure thereof is−Pv1. A difference in pressure therefore occurs between the exterior ofthe endoscope 2 and the interior thereof. The difference in pressurebrings about force oriented from the exterior of the endoscope 2 to theinterior thereof. The pressure regulating value therefore remainsclosed. In this state, the force arising from the difference in pressure(Pac-(−Pv1)) is applied to the waterproof film 43 of the push-buttonswitch 24. As shown in FIG. 2B, the pressing member 42 is displaced bythe distance Xac from the initial reference position thereof, and thusdeformed.

According to the present embodiment, the relationship expressed asformula (1) is established for fear the pressing member 42 may constrainthe switch 41 to move inward in the above state.

The dry step will be discussed below.

At the dry step, the internal pressure of the autoclave becomes negative(the negative pressure shall be abbreviated as −Pv2). At this time, theinternal pressure of the endoscope 2 is also negative and about −Pv1.

Now, the absolute values of the pressures Pv1 and Pv2 will be describedbelow.

The pressure Pv1 is the internal pressure of the endoscope 2 applied atthe completion of the pre-vacuum step. The absolute value of thepressure Pv1 slightly decreases by the start of the dry step. This isbecause the O rings and other seals, which are not shown and areincluded in the endoscope 2, cannot keep the endoscope ideallyabsolutely airtight, and a pressure loss therefore occurs.

On the other hand, the pressure Pv2 is the negative pressure forciblyapplied in the autoclave. The absolute values of the pressures Pv1 andPv2 have the following relationship:

|Pv1|<|Pv2|  (2)

Consequently, the external and internal pressures of the endoscope 2 arenegative. Due to a difference between the absolute values of thepressures, the pressure regulating valve opens and the external andinternal pressures of the endoscope 2 are regulated. When the dry stepis completed, there is no difference in pressure between the exteriorand interior of the endoscope. Nearly equal negative pressure (thenegative pressure shall be abbreviated as −Pav) is applied in theexterior and interior of the endoscope 2. In this state, since adifference in pressure does not occur between the exterior and interiorof the endoscope 2, no force works on the endoscope 2 from the exteriorof the endoscope 2 to the interior thereof. The waterproof film 43 doesnot therefore deform.

When the dry step is completed, the pressure in the autoclave becomesequal to the atmospheric pressure. At this time, the internal pressureof the endoscope 2 remains negative (the internal pressure is −Pavg). Adifference in pressure therefore occurs between the exterior andinterior of the endoscope 2. The difference in pressure brings aboutforce oriented from the exterior of the endoscope 2 to the interiorthereof. The pressure regulating valve therefore remains closed. In thisstate, the force arising from the difference in pressure (Pa-(−Pavg)) isapplied to the waterproof film 43. Consequently, the waterproof film 43deforms as shown in FIG. 2B.

However, the difference in pressure occurring at this time is smallerthan the difference in pressure occurring at the sterilization step. Thedisplacement of the pressing member 42 from the initial referenceposition thereof is smaller than Xac. Therefore, the pressing member 42does not constrain the switch 41 to move inward in this state.

In general, at an institution at which the endoscope 2 is used, theendoscope 2 is usually not put in the autoclave until endoscopicexaminations for a day are all completed. Autoclaving is startedimmediately after use of the endoscope. However, after the autoclavingis completed, the endoscope 2 is usually not taken out of the autoclaveuntil the next morning. Consequently, the endoscope 2 retains in a stateattained at completion of the dry step all night long at the longest. Atthis time, the internal pressure of the endoscope 2 remains negative.Pressure is kept applied to the waterproof film 43 all night long at thelongest.

In a typical autoclave, pressure applied to the waterproof film 43deviates from the atmospheric pressure by a value that falls within therange expressed below.

At the pressurization step:

Pac−(−Pv 1)=approx. +0.27 to +0.29 [MPa]  (3)

At the dry step:

Pa−(−Pavg)=approx. +0.07 to +0.09 [MPa]  (4)

So, the distance Xsp and the hardness of a rubber made into thewaterproof film 43 are set to values that disable the pressing member 42from constraining the switch 41 to move inward when the pressing member42 is moved with a load derived from, for example, 0.3 [Mpa] imposed onthe waterproof film 43. At the same time, the values permit the pressingmember to constrain the switch 41 to move inward when an operatorpresses the waterproof film 43 with his/her finger.

Since the endoscope 2 has the push-button switches 24 that arestructured as mentioned above, advantages described below are provided.

After autoclaving is completed, even if the pressing member 42 isdisplaced toward the switch 41 and the waterproof film 43 is deformedpermanently, the pressing member 42 will not constrain the switch 41 tomove inward. Namely, the switch 41 will not be turned on and held down.

Moreover, after autoclaving is completed, the pressing member 42 willnot constrain the switch 41 to move inward. So, even if the endoscope isleft as it is for a prolonged period of time after being autoclaved, thestem incorporated in the switch 41 is prevented from permanentlydeforming. Consequently, a conduction failure is prevented fromoccurring, and a sense of touch is prevented from deteriorating.

Furthermore, when an autoclave is following the pressurization step, ifthe pressing member 42 does not constrain the switch 41 to move inward,the switch 41 is prevented from being broken due to a load derived frompressure at the pressurization step and a thermal load derived from hightemperature thereat.

Moreover, even when an autoclave designed to follow the dry step isadopted, the initial reference position is determined so that thepressing member 42 will not constrain the switch 41 to move inwarddespite a difference in pressure occurring between the pressurizationstep and decompression step. Consequently, the switch 41 is preventedfrom being broken.

Incidentally, the distance Xsp between the initial reference positionand the switch 41 observed before start of autoclaving, and the hardnessof a rubber made into the waterproof film 43 may be set to values thatpermit the pressing member 42 to constrain the switch 41 to move inwardafter completion of the pressurization step or dry step. At this time,the values permit the pressing member 42 to constrain the switch 41 tomove inward as long as constraining force exerted in constraining theswitch 41 will not cause the stem incorporated in the switch 41 topermanently deform or break down.

In other words, after the pressurization step or dry step is completed,even if the pressing member 42 constrains the switch 41 to move inward,the stem incorporated in the switch 41 shall not permanently deform. Thedistance Xsp and the hardness of a rubber made into the waterproof filmare set to values that meet the above condition and that establish thefollowing relationship:

Xsp<Xac<Xsp+Xsw  (5)

where Xsp denotes the distance between the initial reference position ofthe end of the presser and the top of the switch, Xac denotes adisplacement of the end of the presser from the initial referenceposition, and Xsw denotes a distance covered by one stroke of theswitch.

Herein, a description will be made of the stem that is incorporated inthe switch 41 and that will not permanently deform when the switch 41 isconstrained to move inward by a distance Scr [mm].

In a typical autoclave, pressure applied to the waterproof film 43deviates from the atmospheric pressure by a value expressed as formula(3) or (4).

In other words, when pressure deviating from the atmospheric pressure by0.29 [Mpa] is applied to the waterproof film 43, the pressing member 42shall deform and constrain the switch 41 to move inward by a distanceshorter than Scr [mm].

As mentioned above, when a load derived from, for example, 0.29 [MPa] isimposed on the waterproof film 43, as long as the stem incorporated inthe switch 41 does not permanently deform, the pressing member 42 mayconstrain the switch 41 to move inward after completion of thepressurization step or dry step.

The distance between the initial reference position and the switch 41observed before start of autoclaving and the hardness of a rubber madeinto the waterproof film 43 are set to values that meet the abovecondition. At this time, the values permit the pressing member toconstrain the switch 41 to move inward when an operator presses thewaterproof film 43 with his/her finger.

Consequently, after the pressurization step or dry step is completed inthe autoclave, force oriented from the exterior of the endoscope 2 tothe interior thereof is applied because of a difference in pressurebetween the interior and exterior of the endoscope. The pressing member42 moves toward the switch 41 and constrains the switch 41 to moveinward. The magnitude of constraint is not so large as to permanentlydeform the stem incorporated in the switch 41.

Consequently, an operator is required to press the waterproof film 43 bya short distance. Thus, satisfactory manipulation is offered.

According to the present embodiment, consideration is taken into thepre-vacuum step or dry step at which the pressure in an autoclave isnegative. Some types of autoclaves follow neither the pre-vacuum stepnor the dry step.

When this type of autoclave is used, the external pressure of theendoscope 2 will not be lower than the internal pressure thereof. Forthis reason, the endoscope 2 need not necessarily have the pressureregulating valve. The endoscope 2 should merely be kept watertight andput in the autoclave.

Moreover, the interior of the autoclave is pressurized at thesterilization step (the internal pressure is Pac). The external pressureof the endoscope 2 is Pac, and the internal pressure thereof is Pa. Thisresults in a difference (Pac−Pa) in pressure. At this time, forcearising from the difference in pressure is applied to the waterprooffilm 43. In this case, the distance between the initial referenceposition and the switch 41 observed before start of autoclaving is setto a value dependent on the difference in pressure (Pac−Pa).

As far as a type of autoclave that follows neither the pre-vacuum stepnor dry step is concerned, pressure applied to the waterproof film 43deviates from the atmospheric pressure by a value expressed below.

At the pressurization step:

Pac−Pa=approx. +0.2 [MPa]  (6)

At completion of the pressurization step:

Pa=approx. 0 [MPa]  (7)

When an autoclave that follows neither the pre-vacuum step nor the drystep is used, the distance between the initial reference position andthe switch 41 observed before start of autoclaving, and the hardness ofa rubber made into the waterproof film 43 are set to values that disablethe pressing member 42 from constraining the switch 41 to move inward.At this time, the values should disable the pressing member 42 fromconstraining the switch 41 to move inward when the pressing member 42 isdisplaced with a load derived from 0.2 [MPa] imposed on the waterprooffilm 43. Moreover, the values should permit the pressing member toconstrain the switch 41 to move inward when an operator presses thewaterproof film 43 with his/her finger.

Moreover, when the switch 41 itself makes a stroke (Xsw1) to enter theon state, the distance between the initial reference position and theswitch 41 observed under the atmospheric pressure may be zero. In otherwords, the switch 41 itself may be displaced to physically make a strokeXsw. In order to turn on the switch actually, the switch 41 must bepressed by a distance covered by the stroke Xsw1.

In this case, the distance between the initial reference position andthe top of the switch 41 observed in an atmospheric-pressure environmentis set to a value that has the following relationship:

Xac−Xsw 1 ≦Xsp  (8)

When the switch 41 makes the stroke (Xsw1) to enter the on state, beforethe endoscope is autoclaved, the pressing member 42 may constrain theswitch 41 to move inward by a distance shorter than the distance coveredby the stroke Xsw1.

Moreover, the present invention may be applied to a case where thepressing member 42 does not constrain the switch 41 to move inwardduring autoclaving as mentioned in relation to the foregoing embodiment.Alternatively, the present invention may be applied to a case wherealthough the pressing member 42 constrains the switch 41 to move inwardduring autoclaving, the magnitude of constraint is not so large as tobreak the switch 41. In short, the distance between the initialreference position and the switch 41 obtained before start ofautoclaving, and the hardness of a rubber made into the waterproof film43 are set to values that disable the pressing member 42 from bringingthe switch 41 to the on state. At this time, the values disable thepressing member 42 from bringing the switch 41 to the on state at anytime when the endoscope 2 is reusable for examination after all thesteps of autoclaving are completed.

If the distance between the initial reference position and the switch 41observed before start of autoclaving and the hardness of a rubber madeinto the waterproof film 43 are set to values that disable the pressingmember 42 from constraining the switch 41 to move inward at any step ofautoclaving, no problem will occur. However, in this case, an operatormust exert a large amount of force in manipulating the switch 41 duringendoscopic examination. The operator is thus required to incur a load.An optimal relationship is therefore established according to a purposeor situation of use within the scope of the present invention.

Moreover, according to the present invention, the distance between theinitial reference position and the switch observed before start ofautoclaving, and the hardness of a rubber made into the waterproof film43 are set to values that disable the pressing member 42 fromconstraining the switch 41 to move inward. At this time, the valuedisable the pressing member 42 from constraining the switch 41 to moveinward even if pressure ranging from 0.07 [MPa] to 0.09 [MPa] works onthe endoscope 2 from the exterior of the endoscope 2 to the interiorthereof at the decompression step. When the distance and hardness areset to the values, after the autoclaving is completed, if the pressingmember 42 is displaced toward the switch 41 for a prolonged period oftime, the pressing member 42 will not constrain the switch 41 to moveinward. Consequently, the switch 41 is prevented from being brokenbecause it is constrained to move inward for a prolonged period of time.Moreover, after the pressing member 42 is displaced and cooled, even ifthe pressing member 42 is deformed, the pressing member 42 will notpress the switch 41.

The present invention will not be limited to the aforesaid embodimentbut various variants can be constructed without a deviation from thegist of the present invention.

Referring to FIG. 4A and FIG. 4B, an example of a structure of the resintubes incorporated in the flexible tube will be described below. Theuniversal cord has the same structure as the flexible tube. Therefore,the resin tubes incorporated in the flexile tube will be solelydescribed below. Dot-dash lines in FIG. 4B indicate the initial statesof the resin tubes (denoted by 55).

As shown in FIG. 4A, the flexible tube 15 consists mainly of a spiraltube 51, a braid 52, and a sheathing 53 which are layered in that orderfrom the innermost layer. The spiral tube 51 has a belt-like thinmetallic piece spirally wound. The braid 52 covers the periphery of thespiral tube 51 and is made by plaiting metallic thin wires such asstainless steel wires in the form of a net. The sheathing 53 made of aresin covers the outer surface of the braid 52. Only one spiral tube 51is depicted in FIG. 4A and FIG. 4B. Alternatively, the spiral tube 51may be functionally two-ply or three-ply. Moreover, the sheathing 53 ismade of a resin material, for example, an ester-series thermoplasticelastomer, an amide-series thermoplastic elastomer, a styrene resin, ora fluorocarbon rubber.

A plurality of channels including an aeration/perfusion channel used toperform aeration or perfusion and a therapeutic instrument passagechannel that can also be used to perform suction is formed in theflexible tube 15. These channels are comprised of resin tubes 55 made ofa resin material that is usually based on polytetrafluoroethylene(PTFE).

FIG. 4A and FIG. 4B show four resin tubes 55. Any number of resin tubes55 may be incorporated, and the number of resin tubes 55 may be equal toor smaller or larger than four. Signal lines, a fiber bundle, metallicwires and the like are passed through the flexible tube 15, though theyare not shown in FIG. 4A and FIG. 4B. Signals sent from an imagingdevice incorporated in the distal part 17 of the endoscope 2 aretransmitted over the signal lines. Illumination light is propagated toan illumination lens incorporated in the distal part 17 over the fiberbundle such as a light guide. The metallic wires convey a manipulationthat is performed on the control section 8 in order to angle the distalpart 17.

As shown in FIG. 4A, in an initial state in which the endoscope 2 is notyet put in an autoclave, gaps are present among the resin tubes 55 andbetween the resin tubes 55 and the inner surface of the spiral tube 51of the flexible tube 15.

When the endoscope 2 is autoclaved, after the sterilization step or drystep is completed, a difference in pressure occurs between the interiorand exterior of the endoscope, and force works on the endoscope 2 fromthe exterior of the endoscope 2 to the interior thereof. Consequently,force works on the resin tubes 55 from the centers of the resin tubes tothe peripheries thereof. This is because at least one end of each resintube 55 opens on the space outside the endoscope 2. The force causes theresin tubes 55 to expand to increase their outer diameters.

After the sterilization step or dry step is completed, the resin tubes55 expand to increase their outer diameters. The expansion of the resintubes 55 arises from the difference in pressure between the exterior andinterior of the endoscope 2. Normally, after the dry step is completed,the endoscope 2 is brought to an atmospheric-pressure environment, andthe pressure regulating valve is opened forcibly. Thus, the expandedresin tubes 55 are restored to have their original outer diameters.

However, as far as an existing endoscope is concerned, the resin tubes55 expand while placed in a high-temperature environment at thesterilization step. After the dry step is completed, even if theendoscope is brought to an atmospheric-pressure environment and thepressure regulating valve is forcibly opened, the resin tubes may not berestored to have their original outer diameters. The resin tubes mayhave their outer diameters held increased to be slightly larger than theoriginal outer diameters.

According to the present embodiment, even after the sterilization stepor dry step is completed, it should be so constituted that gaps arepresent among the resin tubes 55 and between the resin tubes 55 and theinner surface of the spiral tube 51.

Therefore, the sizes of the gaps among the resin tubes 55 observed inthe initial state and the sizes of the gaps between the resin tubes 55and the inner surface of the spiral tube 51 observed therein are set tovalues that permit gaps to lie, as shown in FIG. 4B, among the resintubes 55 and between the resin tubes 55 and the inner surface of thespiral tube 51 even after completion of the sterilization step or drystep.

For setting the sizes of the gaps to the values, it is necessary toquantitatively grasp a magnitude of expansion by which the resin tubes55 expand to increase their outer diameters after completion of thesterilization step or dry step. The magnitude of expansion isexperimentally obtained by subjecting a unit resin tube 55 to the samedifference in pressure as the difference in pressure occurring aftercompletion of the sterilization step or dry step.

In a typical autoclave designed to perform decompression at thepre-vacuum step or dry step, pressure applied to the endoscope 2 fromthe exterior of the endoscope 2 to the interior thereof deviates fromthe atmospheric pressure by a value that falls within a following range:

At the pressurization step:

+0.27 to +0.29 [MPa]  (9)

At completion of the dry step:

+0.07 to +0.09 [MPa]  (10)

Consideration should therefore be taken into a case where the appliedpressure is higher than the atmospheric pressure. For example, pressurethat is higher than the atmospheric pressure by 0.3 [MPa] is applied tothe unit resin tube 55 from the center of the tube to the peripherythereof, and a magnitude of expansion caused by the application of thepressure can be measured. In consideration of the magnitude ofexpansion, the sizes of the gaps present in the initial state are set tovalues that permit presence of gaps even after completion of thesterilization step or dry step.

Some types of autoclaves are designed to follow neither the pre-vacuumstep nor the dry step. In such an autoclave, pressure working on theendoscope 2 from the exterior of the endoscope 2 to the interior thereofdeviates from the atmospheric pressure by a value presented below.

At the pressurization step: +0.2 [MPa]

At completion of the pressurization step: 0 [MPa] Consideration istherefore taken into a case where the applied pressure is higher thanthe atmospheric pressure. For example, pressure higher than theatmospheric pressure by 0.2 [MPa] is applied to the unit resin tube 55from the center of a unit resin tube 55 to the periphery thereof, and amagnitude of expansion caused by the application of the pressure ismeasured. In consideration of the magnitude of expansion, the gapspresent in the initial state are set to proper values.

Moreover, normally, pressure higher than the atmospheric pressure by 0.3[MPa] is applied to perform a test and a magnitude of expansion causedby the application of the pressure is taken into account in order to setthe gaps present in the initial state to proper sizes, so that anyautoclave could be used to sterilize the endoscope 2.

Consequently, even after the sterilization step or dry step iscompleted, gaps are present among the resin tubes 55 and between theresin tubes 55 and the inner surface of the spiral tube 51. When theflexible tube 15 is bent, the resin tubes 55 can freely move in thelongitudinal direction of the flexible tube 15. No load is thereforeimposed on fixtures attached to the ends of the resin tubes 55. Evenwhen the resin tubes 55 expand, the other built-in components isprevented from being pressured.

Consequently, an occurrence rate of a defect such as water leakagederived from breakage of the fixture attached to the end of any resintube can be reduced. Moreover, the other built-in components will not bebroken.

According to the aforesaid embodiment, the sizes of the gaps present inthe initial state are set to proper values in consideration of amagnitude of expansion by which the resin tubes 55 expand aftercompletion of the sterilization step or dry step. Some types of flexibletubes 15 may contract to decrease their inner diameters after completionof the sterilization step or dry step. Consideration is therefore takeninto not only the magnitude of expansion by which the resin tubes 55expand at completion of the sterilization step or dry step but also amagnitude of contraction by which the flexible tube 15 contracts todecrease its inner diameter after completion of the sterilization stepor dry step when the initial state is set to proper value.

In order to set the sizes of the gaps present in the initial state toproper values, consideration must be taken into the magnitude ofexpansion by which the resin tubes 55 expand to increase their outerdiameters after completion of the sterilization step or dry step, andthe magnitude of contraction by which the flexible tube 15 contracts todecrease its inner diameter. The magnitude of contraction is obtainedexperimentally similarly to the magnitude of expansion by which theresin tubes 55 expand to increase their outer diameters at completion ofthe sterilization step or dry step. Specifically, an experiment isperformed to measure the magnitude of contraction by subjecting a unitflexible tube 15 to the same difference in pressure as the difference inpressure occurring at completion of the sterilization step or dry step.

In a typical autoclave, pressure applied to the endoscope 2 from theexterior of the endoscope 2 to the interior thereof deviates from theatmospheric pressure by a value expressed with formula (9) or (10).

Consideration is therefore taken into a case where the applied pressureis higher than the atmospheric pressure. For example, pressure higherthan the atmospheric pressure by 0.3 [MPa] is applied to the unitflexible tube 15 from the exterior of the unit flexible tube 15 to theinterior thereof. A magnitude of contraction by which the flexible tubecontacts at that time is measured. In consideration of the magnitude ofcontraction, the sizes of the gaps present in the initial state are setto values that permit presence of gaps among the built-in componentseven after completion of the sterilization step or dry step.

Even for a type of autoclave designed to omit the pre-vacuum step anddry step, the magnitude of expansion obtained experimentally using aunit resin tube 55 is applied.

Moreover, in the aforesaid embodiment, the sizes of the gaps among theresin tubes 55 and the gaps between the resin tube 55 and the innersurface of the spiral tube 51 which are observed in the initial stateare set to values that permit presence of gaps among the resin tubes 55and between the resin tubes 55 and the inner surface of the spiral tube51 after completion of the sterilization step or dry step.

However, gaps must be present among the resin tubes 55 and between theresin tubes 55 and the inner surface of the spiral tube 51 even aftercompletion of the dry step. At the sterilization step, gaps may notnecessarily be present as long as the other built-in components will notbe broken.

At the sterilization step, as long as the resin tubes 55 and the otherbuilt-in components are not pressured to be broken, they may deform abit. However, gaps must be present among the resin tubes 55 and betweenthe resin tubes 55 and the inner surface of the spiral tube 51 aftercompletion of the dry step. The sizes of the gaps among the resin tubes55 and between the resin tubes 55 and the inner surface of the spiraltube 51 that are present in the initial state are set to values thatpermit presence of gaps among the resin tubes 55 and between the resintubes 55 and the inner surface of the spiral tube 51 after completion ofthe dry step.

In a typical autoclave, pressure applied to the endoscope 2 from theexterior of the endoscope 2 to the interior thereof deviates from theatmospheric pressure by a value expressed in formula (9) or (10).

Consideration is therefore taken into a case where the applied pressureis higher than the atmospheric pressure. For example, pressure higherthan the atmospheric pressure by 0.3 [MPa] is applied to a unit flexibletube 15 from the periphery of the tube to the center thereof. Amagnitude of expansion of the resin tubes 55 and a magnitude ofcontraction of the flexible tube 15 that arise from the application ofthe pressure are then measured. At the same time, magnitudes ofdeformation by which the resin tubes and the other built-in componentsdeform to break down are experimentally measured in advance. Thesemagnitudes are taken account in order to set the sizes of the gapspresent in the initial state to proper values.

The endoscope 2 may be transported after completion of the dry step.Therefore, when no gaps are present among the resin tubes 55 and betweenthe resin tubes 55 and the inner surface of the spiral tube 51, if theinsertion member 7 is bent during the transportation, the built-incomponents may be broken because they cannot move relative to oneanother. However, the endoscope 2 will not be moved at the sterilizationstep. Therefore, at the sterilization step, the resin tubes may deform abit to have no gaps among them as long as they will not pressure theother built-in components.

In other words, when the sterilization step is under way in anautoclave, the resin tubes 55 expand, and no gaps are present among theresin tubes 55 and between the resin tubes 55 and the inner surface ofthe spiral tube 51. After completion of the dry step, gaps are presentamong the resin tubes 55 and between the resin tubes 55 and the innersurface of the spiral tube 51.

Consequently, no gaps are present at the sterilization step. However,after completion of the dry step, the internal pressure of the endoscopeis retained at a negative value of −0.09 [MPa] at most owing to theoperation of the pressure regulating valve. Even when the resin tubes 55expand and the flexible tube 15 contracts, gaps are present among theresin tubes 55 and between the resin tubes 55 and the inner surface ofthe spiral tube 51. Even when the endoscope 2 is transported ormanipulated anyhow, the endoscope 2 will not be broken.

Referring to FIG. 5A and FIG. 5B, an example of the structure of thebreakage-of-insertion member preventing member will be described below.

The breakage-of-control section preventing member andbreakage-of-connector unit preventing member have the same structure asthe breakage-of-insertion member preventing member. The structure of thebreakage-of-insertion member preventing member alone will be described,but the description of the other anti-breakage members will be omitted.

As shown in FIG. 5A, a seal portion 60 included in the endoscope 2 isengaged with the periphery of the flexible tube 15 in order to keep theflexible tube fluid-tight at least in an atmospheric-pressureenvironment. The inclusion of the seal portion 60 creates a space 61between the breakage-of-insertion member preventing member 12 adjoiningthe control section 8 and the periphery of the flexible tube 15. Theseal portion 60 is engaged with the periphery of the flexible tube 15 inorder to keep the flexible tube 15 fluid-tight. At least in theatmospheric-pressure environment, fluid will not invade from theexterior of the endoscope 2 to the interior thereof.

In order to mechanically fix the breakage-of-insertion member preventingmember 12 to the flexible tube 15, a connection pipe 62 and an insertmember 63 are included. The connection pipe 62 is fixed to the sheathing53 of the flexible tube 15 using an adhesive or the like. The insertmember 63 is fixed to the breakage-of-insertion member preventing member12 using an adhesive or the like, or molded as an integral part of thebreakage-of-insertion member preventing member 12.

The connection pipe 62 and insert member 63 each have a screw threadedthereon so that they can be joined firmly. In general, the connectionpipe 62 and insert member 63 are made of metallic materials. The insertmember 63 is also engaged with the control section 8. A sealing membersuch as an O ring 64 is generally interposed between the insert member63 and the control section 8.

In the course of cleaning an endoscope, the endoscope 2 may be immersedin a cleaning solution or water filled into a cleaning vessel that isnot shown. In this case, pressure exerted by the cleaning solution orwater works on the endoscope 2 from the exterior of the endoscope 2 tothe interior thereof. However, the pressure is so negligible that theendoscope is held almost in the same state as the state shown in FIG.5A.

In an environment in which the external pressure of the endoscope 2 islower than the internal pressure thereof, force works on the endoscope 2from the interior of the endoscope 2 to the exterior thereof. The forceoriented from the interior of the endoscope 2 to the exterior thereofarises from pressure applied at the dry step of autoclaving. Pressurelarger than the atmospheric pressure by a value ranging from 0.07 to0.09 [MPa] works on the endoscope 2 from the interior of the endoscope 2to the exterior thereof. Pressure that is higher than the atmosphericpressure by 0.05 [MPa] and oriented from the interior of the endoscope 2to the exterior thereof brings about force smaller than the forceoriented from the interior of the endoscope 2 to the exterior. When thepressure higher than the atmospheric pressure by 0.05 [MPa] works on theendoscope 2, the seal portion 60 separates from the periphery of theflexible tube 15. The inner diameter, thickness, and material of theseal portion 60 of the breakage-of-insertion member preventing member 12are set to values that permit the separation of the seal from theperiphery of the flexible tube. As the material of the seal portion 60,a resin material such as a fluorocarbon rubber is widely adopted.

When the endoscope 2 having the foregoing structure is autoclaved, theendoscope 2 is exposed to a high-temperature high-pressure steamenvironment at the sterilization step. Steam may infiltrate through theseal portion 60 and breakage-of-insertion member preventing member 12,and eventually invade into the space 61. However, when the pressure inthe autoclave becomes negative at the dry step, the seal portion 60 ofthe breakage-of-insertion member preventing member 12 separates from theperiphery of the flexible tube 15. The steam having invaded into thespace 61 is effectively discharged to outside the endoscope 2.

Consequently, at the dry step of autoclaving, the steam having invadedinto the space 61 is effectively discharged to outside. The connectionpipe 62 and insert member 63 that are made of metallic materials willtherefore not corrode.

According to the aforesaid embodiment, the inner diameter, thickness,and material of the seal portion 60 of the breakage-of-insertion memberpreventing member 12 are set to values that permit separation of theseal portion 60 from the periphery of the flexible tube 15 due tonegative pressure occurring at the dry step of autoclaving.

However, some types of autoclaves are designed to omit the pre-vacuumstep and dry step, that is, steps at which the pressure in the autoclavebecomes negative. When such an autoclave is used to sterilize theendoscope 2, steam having invaded into the space 61 at the sterilizationstep will not be discharged. This leads to corrosion of the connectionpipe 62 and insert member 63 that are made of metallic materials.

Therefore, the endoscope 2 is structured so that even when an autoclavedesigned to omit the dry step is used to sterilize the endoscope 2,steam having invaded into the space 61 can be discharged.

Specifically, the inner diameter, thickness, and material of the sealportion 60 of the breakage-of-insertion member preventing member 12 areset to values that permit separation of the seal portion 60 from theperiphery of the flexible tube 15 when pressure higher than theatmospheric pressure by 0.05 [MPa] works on the endoscope 2 from theinterior of the endoscope 2 to the exterior thereof.

Moreover, after the autoclaving is completed, the endoscope 2 has steamleft in the space 61. The endoscope 2 is therefore put in a pressurecontainer that is connected to a suction device capable of performingsuction by means of pressure of 0.1 [MPa] or more. The pressure in thepressure container is set to a value that is smaller than theatmospheric pressure by 0.1 [MPa], that is, made negative.

The seal portion 60 is designed so that when pressure higher than theatmospheric pressure by 0.05 [MPa] works on the endoscope 2 from theinterior of the endoscope 2 to the exterior thereof, the seal portion 60will separate from the periphery of the flexible tube 15. As long as thepressure in the pressure container is set to the negative pressure, theseal portion 60 separates from the periphery of the flexible tube 15.

When the endoscope 2 having the aforesaid structure is autoclaved, theendoscope 2 is placed in a high-temperature high-pressure steamenvironment at the sterilization step. Steam may invade into the space61 through the seal portion 60 and breakage-of-insertion memberpreventing member 12. In this case, when an autoclaving process devoidof the dry step is adopted, the steam is left intact in the space 61 atcompletion of autoclaving. However, thereafter, if the endoscope 2 isput in the pressure container that is set to the predetermined negativepressure, the seal portion 60 separates from the periphery of theflexible tube 15. Consequently, the steam having invaded into the space61 at the sterilization step is discharged to outside.

The breakage-of-insertion member preventing member 12 is engaged withthe periphery of the flexible tube 15 in order to keep the flexible tube15 fluid-tight. Noted is that the present invention is not limited tothe combination of the breakage-of-insertion member preventing member 12and flexible tube 15. The present invention can apply to the combinationof an elastic member having a seal portion and the surface of thehousing of an endoscope.

Moreover, according to the present embodiment, an elastic member isengaged with the surface of the housing of an endoscope in order to keepthe endoscope fluid-tight at least under the atmospheric pressure.Alternatively, the elastic member may be merely engaged with the surfaceof the housing of an endoscope but not be engaged therewith in order tokeep he endoscope fluid-tight. However, the elastic member has a sealportion that keeps the endoscope fluid-tight when brought into closecontact with the endoscope. In short, when the endoscope 2 is placedunder predetermined pressure oriented from the inner surface of theendoscope 2 to the outer surface thereof, the elastic member separatesfrom the surface of the housing of the endoscope. This allows dischargeof steam that has invaded into a space between the elastic member andthe surface of the housing of the endoscope at the sterilization stepfollowed by an autoclave. Namely, the seal portion 60 is designed toseparate from the surface of the housing of the endoscope 2.

According to the present invention, a wide range of differentembodiments can be constructed based on the invention without adeparture from the spirit and scope of the invention. Moreover, thepresent invention will be limited to the appended claims but notrestricted to any specific embodiments.

What is claimed is:
 1. An endoscope suitable for autoclaving comprising:a flexible tube that contracts to decrease its inner diameter whenpressure or a thermal load is applied or imposed at a pressurizationstep of autoclaving; and a plurality of elongated resin tubesincorporated in the flexible tube that expand to increase their outerdiameter when pressure or a thermal load is applied or imposed at thepressurization step of autoclaving; wherein gaps are set beforehandbetween the plurality of resin tubes and between each resin tube and aninner surface of the flexible tube so that such gaps will be presentafter completion of autoclaving between the plurality of resin tubes andbetween each resin tube and the inner surface of the flexible tube. 2.An endoscope according to claim 1, wherein the gaps will be presentbetween the plurality of resin tubes and between each resin tube and theinner surface of the flexible tube even at the pressurization step ofthe autoclaving.
 3. An endoscope according to claim 1, wherein the gapswill be present between the plurality of resin tubes and between eachresin tube and the inner surface of the flexible tube even at adecompression step of the autoclaving.
 4. An endoscope according toclaim 1, wherein the gaps will be present between the plurality of resintubes and between each resin tube and the inner surface of the flexibletube even if a difference in pressure occurring between thepressurization step of the autoclaving and a decompression step thereoffunctions on the resin tubes and the flexible tube.
 5. An endoscopesuitable for autoclaving comprising: a flexible tube that contracts todecrease its inner diameter when pressure or a thermal load is appliedor imposed at a pressurization step of autoclaving; a plurality ofelongated resin tubes incorporated in the flexible tube that expand toincrease their outer diameter when pressure or a thermal load is appliedor imposed at the pressurization step of autoclaving; wherein gaps areset beforehand between the plurality of resin tubes and between eachresin tube and an inner surface of the flexible tube so that such gapswill be present after completion of autoclaving between the plurality ofresin tubes and between each resin tube and the inner surface of theflexible tube; and the gaps after the completion of autoclaving enableeach resin tube to move freely in a longitudinal direction with respectto the resin tube when the flexible tube is bent.
 6. An endoscopeaccording to claim 5, wherein the gaps will be present between theplurality of resin tubes and between each resin tube and the innersurface of the flexible tube even at the pressurization step of theautoclaving, and the gaps at the pressurization step of the autoclavingenable each resin tube to move freely in the longitudinal direction whenthe flexible tube is bent.
 7. An endoscope according to claim 5, whereinthe gaps will be present between the plurality of resin tubes andbetween each resin tube and the inner surface of the flexible tube evenat a decompression step of the autoclaving, and the gaps at thedecompression step of the autoclaving enable each resin tube to movefreely in the longitudinal direction when the flexible tube is bent. 8.An endoscope according to claim 5, wherein the gaps will be presentbetween the plurality of resin tubes and between each resin tube and theinner surface of the flexible tube even if a difference in pressureoccurring between the pressurization step of the autoclaving and adecompression step thereof functions on the resin tubes and the flexibletube, and the gaps at the decompression step of the autoclaving enableeach resin tube to move freely in the longitudinal direction when theflexible tube is bent.